I find that magnets do everything I need to hold materials down, and have yet to need a pin for the crumb tray. I use bar magnets to butt thick materials against and bars or discs to hold thinner materials in place, depending on the desired effect.
Keep in mind that the crumb tray can move, so you won’t get perfect registration with pins/pegs in the tray. From where I stand, that’s the only use case that comes to mind for pins, and it just can’t work.
What sort of thing do you need pins for? I bet there’s a use case I am not considering or haven’t come across yet.